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Publication numberUS5433300 A
Publication typeGrant
Application numberUS 08/211,221
Publication dateJul 18, 1995
Filing dateSep 22, 1992
Priority dateSep 25, 1991
Fee statusLapsed
Also published asDE69214830D1, DE69214830T2, EP0605530A1, EP0605530B1, WO1993006382A1
Publication number08211221, 211221, US 5433300 A, US 5433300A, US-A-5433300, US5433300 A, US5433300A
InventorsJohn Barlow, Philip J. Smith
Original AssigneeG.K.N. Sankey Ltd.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Brake caliper
US 5433300 A
Abstract
A brake caliper has the effective modulus of elasticity of the material increased by inserting a honeycomb-like ceramic piece made of a material having a higher modulus of elasticity in a die and casting metal to fill the die, substantially encase the ceramic and substantially fill the pores of the same, and squeeze forming the molten metal to ensure substantial filling of the pores of the ceramic.
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Claims(9)
We claim:
1. Brake caliper construction comprising:
a squeeze-formed casting of light alloy metal material having a predetermined modulus of elasticity and predetermined areas thereof designated to receive secondary machining by a machine tool following casting and adjacent areas known not to require such secondary machining;
at least one preformed porous ceramic honeycomb insert cast in place within said casting having a modulus of elasticity relatively greater than that of said light alloy metal and being impregnated with said light alloy material as a result of the squeeze casting process, and wherein said at least one insert is shaped and located within said adjacent areas in spaced relation to said predetermined areas so as to avoid being contacted by the machine tool during the performance of secondary machining on said predetermined areas.
2. The construction of claim 1 wherein said casting includes a pair of laterally spaced side portions for location on opposite sides of a brake disc and a pair of spaced end portions interconnecting said side portions for straddling the disc, and at least another preformed porous ceramic insert, said inserts are symmetrical in configuration and provided in each of said end portions in spaced relation to one another.
3. The construction of claim 1 wherein said insert comprises a plurality of discrete ceramic particles pressed-formed to shape and having a predetermined volumetric percentage of voids that renders said insert porous.
4. The construction of claim 1 wherein said insert is constructed according to a lost foam process in which a slurry of ceramic material is introduced into voids of a preform foamed material and the slurry and preform thereafter are heated sufficiently to destroy the preform and harden the slurry to produce a resultant ceramic insert having a predetermined volumetric percentage of voids.
5. The construction of claim 4 wherein said preform is constructed from individual sheets of the foamed material joined to one another and formed to the required shape.
6. The construction of claim 4 or 5 wherein said insert has at least 20% voids.
7. The construction of claim 4 or 5 wherein said insert has at least 30% voids.
8. The construction of claim 4 or 5 wherein said insert has at least 40% voids.
9. The construction of claim 4 or 5 wherein said insert has at least 50% voids.
Description

This invention relates to brake calipers for so called disc brakes primarily for motor vehicles.

BACKGROUND OF THE INVENTION

DE 29 50 660--A proposes a brake caliper having cast in reinforcement parts made of a higher strength material which may be steel, hard metal or ceramic.

JP 59-123997--A provides a rocker arm made as an aluminium alloy casting with a sintered body of porous ceramics disposed in the pad position of the rocker arm, and made by locating the sintered body into the mould and filling the mould with molten alloy under high pressure and maintaining the pressure until the alloy solidifies.

The designer of a brake caliper is particularly concerned to provide stiffness, so that when the brake pads are forced against the disc the caliper will not deform under load and hence reduce or vary the pad pressure distribution. The problem in providing adequate stiffness is due to the overall limitations of space availability especially when the caliper is within a wheel, as well as the restrictions of available materials on inherent stiffness, cost and weight limitations.

For high duty purposes, for example racing car brakes, the caliper is usually made of an aluminium alloy or a so-called composite material in which particles or fibres of silicon carbide or the like are distributed uniformly through the metal: this composite-material does indeed have an improved modulus of elasticity but is extremely difficult to machine because the silicon carbide is not only stiffer but is extremely hard and tends to damage cutting tools. The cutting rates, lubricant requirements and so forth for the aluminium matrix and ones which might suit the silicon carbide are widely different.

The object of the invention is to provide improved stiffness whilst enabling the necessary machining to be carried out.

SUMMARY OF THE INVENTION

According to the present invention, a brake caliper comprises a light alloy casting incorporating one or more reinforcements made of a material having a higher modulus of elasticity than that of the light alloy and surrounded by the light alloy, and is characterised in that the reinforcements are of honeycomb-like ceramic which is impregnated with the alloy by squeeze-forming the molten metal in the casting die, and in that said reinforcements are located in areas of the cast caliper where machining is not required.

Squeeze forming is a technique developed by GKN Technology Limited and which, for the purposes of the present invention, comprises making a metal casting in matched punch and die and applying continuing pressure to the metal in the die during the solidification of the molten metal. This avoids cavities from shrinkage, and may give improved grain structure. The quality of the cast component may approach that of a forged component when squeeze forming is used.

According to the invention from a second aspect, a brake caliper comprises a light metal alloy casting incorporating a honeycomb-like ceramic insert impregnated with the alloy, the insert being located in positions where machining is not required. Because the insert is of a discrete shape, instead of being distributed uniformly throughout the whole of the material from which the caliper is made, the problem with machining can be avoided.

Preferably both features are employed in a single caliper, that is to say the ceramic insert is used in a squeeze formed casting.

The ceramic insert may be made in various ways.

According to one possibility, ceramic particles are formed into a shape by pressing in a die preferably followed by a heat treatment to fuse the particles into the shape. The particles may be screened before pressing to reject unacceptably small particles or fines that pass through the screen so as to control particle size; and thus the resultant volume percentage of voids produced in the ceramic insert. Preferably the voids total of the order of 50% of volume of the shape, although lower values of voids are also useful.

According to a second possibility, a porous foamed resin shape is created for example by moulding the foam, or by cutting from a sheet or block of foam, and/or by building up a shape from a series of cut pieces of foam. The shape is then filled with a ceramic slurry, dried, and fired. The firing destroys the foam and leaves the required voids and may improve the handleability of the ceramic. The same 50% porosity is the aim, but suitable foams for this purpose with such a high degree of porosity tend to be weak, and lower levels of porosity may have to be accepted if this technique is used, for this reason

A third possibility is to cast a slurry mix of ceramic and a lower melting point material, dry the casting, machine it (if required) to the final shape, and then fire it to melt out all the low melting point component of the original mix and leave the required porous ceramic shape.

Other methods of creating the porous ceramic may be used.

The object of the ceramic is to add material of a higher modulus of elasticity than that of the metal. The ceramic may be of a lower weight so that stiffness is increased without increasing weight, or even if it is of a higher specific gravity, it is only added in discrete areas and not over the whole of the casting and consequently advantage may still be attained.

Aluminium and its alloys typically have a modulus of elasticity of about 70-75 whereas alumina has a modulus of about 300: these figures however are at typical temperate zone ambient day temperatures, whereas racing car brakes often run at over 200 deg.C. At such elevated temperatures the modulus of the alloy drops sharply, for example halves, whereas that of alumina is hardly affected.

Other possible ceramics for use in the invention are alumina-zirconia, alumina-silicate, silica nitride and silicon carbide. The selected material is to be one which does not dissolve in the casting metal during the casting process which may involve considerations of both time, temperature and pressure, so as to avoid dispersion of the ceramic in the metal, but otherwise the higher the modulus, when all other parameters remain the same, the better the result. At present the inventors prefer the combination of aluminium and alumina.

The ceramic form is suitably shaped and dimensioned to be supported in the die so that its porosities become filled with the metal during the casting and squeeze forming process.

The ceramic form is to be located in positions in the caliper avoiding areas which are to be drilled or otherwise machined so that any machining processes carried out are only on the alloy and not on the ceramic.

Experimental results show that a brake caliper made in the manner herein described with the squeeze-formed metal casting and a ceramic insert having about 30% voids before location in the casting had a modulus of elasticity increased by some 40%.

THE DRAWINGS

One embodiment of the invention is now more particularly described with reference to the accompanying drawing wherein.

FIG. 1 is a somewhat diagrammatic and sectional elevation showing squeeze forming carried out on a brake caliper casting:

FIG. 2 is a plan view of a typical brake caliper casting:

FIG. 3 is an elevation of the same from one side;

FIG. 4 is a part sectional elevation and also showing the other side;

FIG. 5 is a plan view of a ceramic component

FIG. 6 is a section taken on the line 6--6 of FIG. 5: and

FIG. 7 is an end elevation of the component of FIGS. 5 and 6

DETAILED DESCRIPTION

Turning now to the drawings, FIG. 1 shows the basic squeeze forming technique in which a mould part 10 is formed with one half of the shape of the required casting and a mould part 12 is formed with the other half of the required shape, the space 14 therebetween is injected with the molten material, in the present case with the ceramic preforms inserted therein, and pressure is applied in the direction of the arrow 16. Squeeze forming is a technique well known per se and needs no further description in the specification.

Turning now to FIGS. 2 to 4, these show a typical brake caliper for a racing car, but some of the finer points in machined holes for example to fix the caliper in position are omitted from the drawing in the interests of clarity. Essentially the caliper comprises a loop with two sides generally indicated by the references 20 and 22 which lie on opposite sides of the plane P which is the plane of the brake disc. These sides are joined by ends, generally indicated by reference numerals 24 and 26 and the ends straddle the disc so as to connect the two sides together. As well understood by those skilled in the brake design art, brake pads of suitable friction material are located against the face of the disc and urged against the disc by hydraulically displaced pistons and the reaction attempts to force the sides apart in the directions of the arrows 30.

The bores which receive the hydraulic components are indicated by the reference numerals 32 34 in FIG. 3.

In this instance two separate but identical ceramic components are provided, shown in plan view in FIG. 2 by the chain dot lines and indicated by the reference numerals 36 38. The same reference numerals are used in FIG. 4 indicating the profile of the inserts.

Turning next to FIGS. 5 to 7, the precise shape of a relatively complex insert as used in FIGS. 2 to 4 is illustrated. The arc 40 FIG. 6 is also seen in FIG. 4 and is concentric to the bore 34 which is to be machined in the casting but leaving a substantial thickness of cast metal about that machine bore in order to contain hydraulic pressure. At other points, for example on the surfaces 42-50 FIG. 6 the insert is to be encased by relatively thinner areas of solid cast metal as seen in FIG. 4, and on the surface 52 FIG. 6 the insert lies closest in relation to the surface of the casting.

In general, in all areas where precision machining is to be carried out on the caliper, the ceramic is shaded to clear the machining, for example in the areas 54 56 FIG. 7. Preferably the insert is arranged to make line contact with the die in places where machining is inessential, for the purpose of locating the insert in the die.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4932099 *Oct 17, 1988Jun 12, 1990Chrysler CorporationMethod of producing reinforced composite materials
US4947924 *Mar 1, 1989Aug 14, 1990Sumitomo Metal Industries, Ltd.Ceramic particles in cobalt matrix
US4995443 *Feb 8, 1989Feb 26, 1991The Board Of Trustees Of Western Michigan UniversityProcess for evaporative pattern casting
DE2950660A1 *Dec 15, 1979Jul 2, 1981Teves Gmbh AlfredBremssattel fuer eine teilbelag-scheibenbremse
EP0440093A1 *Jan 24, 1991Aug 7, 1991Isuzu Motors LimitedCast product having ceramics as insert and method of making same
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JPS61123997A * Title not available
JPS62151650A * Title not available
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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5685398 *Jun 28, 1996Nov 11, 1997Rexnord CorporationFast response adjustable brake
US5730205 *Jul 15, 1996Mar 24, 1998Thomas; Robert AnthonyDie assembly for squeeze casting
US5887684 *Aug 17, 1995Mar 30, 1999Itt Manufacturing Enterprises, Inc.Disk brake calliper
US5906235 *Mar 31, 1997May 25, 1999Thomas Robert AnthonyPressurized squeeze casting apparatus and method and low pressure furnace for use therewith
US6427754 *Jun 21, 1997Aug 6, 2002Honsel AgProcess and device for producing a brake drum or brake disc
US6719104 *Dec 28, 2001Apr 13, 2004Kelsey-Hayes CompanyComposite caliper for a disc brake assembly and method for producing same
US7614340Feb 9, 2007Nov 10, 2009Honeywell International Inc.Composite piston housing for aircraft brakes
DE19647999A1 *Nov 20, 1996May 28, 1998Teves Gmbh AlfredBrake saddle used in road vehicle
DE102008002538A1Jun 19, 2008Dec 3, 2009Robert Bosch GmbhBremssattel aus mindestens 2 Komponenten
DE102012012675A1Jun 23, 2012Dec 24, 2013Daimler AgBrake caliper for disc brake system used in motor car, has stiffening element that is embedded into brake caliper portion and connected along portion of boundary surface with material-brake caliper portion
EP1069332A2 *Jul 3, 2000Jan 17, 2001Sumitomo Electric Industries, LimitedDisk brake with improved caliper
WO2003089169A1 *Apr 17, 2003Oct 30, 2003Drm Druckguss GmbhLight metal cast part with integrated reinforcement material
WO2008052834A1Sep 11, 2007May 8, 2008Bosch Gmbh RobertMethod for producing a body consisting of metal-ceramic-composite materials
Classifications
U.S. Classification188/73.1, 188/370, 188/218.0XL
International ClassificationF16D65/02, F16D55/224, F16D55/00, F16D55/22, B22D19/14, F16D55/228
Cooperative ClassificationF16D2055/0016, F16D55/22, F16D55/228, B22D19/14, F16D2250/0015
European ClassificationF16D55/228, F16D55/22, B22D19/14
Legal Events
DateCodeEventDescription
Sep 16, 2003FPExpired due to failure to pay maintenance fee
Effective date: 20030718
Jul 18, 2003LAPSLapse for failure to pay maintenance fees
Feb 5, 2003REMIMaintenance fee reminder mailed
Jan 11, 1999FPAYFee payment
Year of fee payment: 4
Jun 6, 1994ASAssignment
Owner name: ALCON COMPONENTS LIMITED, ENGLAND
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:BARLOW, JOHN;SMITH, PHILLIP J.;REEL/FRAME:007012/0781
Effective date: 19940318
Owner name: G.K.N. SANKEY LTD., ENGLAND